Hypertension is one of the major cardiovascular diseases in humans. To date, only one animal model has been investigated extensively for this disease, that is, the Okamoto-Aoki spontaneous hypertensive rat. There are several rat and mouse strains which have been shown to have genetic or salt-dependent hypertension. All of these animal models for hypertension may not completely mimic essential hypertension in the human. We have been inbreeding the golden Syrian hamster (Mesecricetus auratus) and we find that strains characterized by their phenotypic traits develop (8-12 wks) and maintain (1-2 yrs) an elevated arterial blood pressure. Thus, one aim of this proposal is to continue the development of these strains of spontaneously hypertensive hamsters (SHH) and their normo- and hypertensive counterparts. Another aim of this proposal is to characterize the central hemodynamics, the renin-angiotensin system and renal function in this new model of hypertension and to compare these same measurements with the renovascular model of hypertension in the hamster and with the data from the SHR. In most forms of hypertension, alterations in the controlling mechanisms for blood pressure and flow in small blood vessels (microcirculation) either lead to the development and/or maintenance of the elevated blood pressure. Thus, one major aim of this proposal is to study the microvasculature in the SHH and its controls by investigating hormonal, neural, and autoregulatory controlling mechanisms for blood pressure and flow and to compare these measurements with those in adrenergically innervated and non-innervated tissue. This combination of macro- and microcirculatory studies will enable us to describe the relative contributions of the microvessels to the developmental and maintenance phases of hypertension in this model. Future goals relate to the possible establishment of the spontaneously hypertensive hamster as a model for the study of genetic hypertension and due to the unique aspect of the cheek pouch of the hamster for allografting tissues, investigating cross-transplantation of tissues from normal and hypertensive hamsters as it relates to their vascular responses. Basic information concerning control of microcirculatory hemodynamics will be obtained and hopefully provide new insights into these physiological processes in normal and hypertensive states.